FIG. 13 shows a conventional curtain structure without drawstrings, including a curtain unit (40) having an upper beam (41) with a receiving space (411), and a string controller (42) is inside the receiving space (411). A spring is in the string controller (42) and can be extended to have a string collecting body (421). A guiding unit (43) is disposed on both sides of the receiving space (411) corresponding to the string collecting body (421), and the guiding unit (43) has two restricting rail stick (431). The string collecting body (421) passes through the guiding unit (43) to connect curtain pieces (44), and is finally secured at a weighted piece (45), whose weight is corresponding to the spring, so that the weighted piece (45) and spring can be balanced and the curtain pieces (44) can expand and restore by pulling or pushing the weighted piece (45). However, the structure of the string controller (42) is complicated and the weighted piece (45) has to be used corresponding to the spring, so it may be difficult to control the curtain unit (40). Also, when the string collecting body (421) passes through the guiding unit (43), it has to circle between the two restricting rail stick (431), which makes the entire assembly process difficult and may increase the costs during assembly process. Therefore, there remains a need for a new and improved curtain structure to overcome the problems stated above.